The standard practice in cell culture is to employ a CO.sub.2 incubator to provide the gaseous atmosphere and temperature control required in static culture processes. These processes include the use of multiwell plates, culture dishes, flasks and the like. The relatively large size of standard CO.sub.2 incubators (with an inside working volume of about 19 in. wide.times.26 in. high.times.19 in. deep), has been used to accommodate small scale processes employing perfusion and mixing equipment, such as pumps and roller mills. Besides being highly inconvenient, such use of CO.sub.2 incubators require substantial capital expenditures and space utilization.
From a process efficiency standpoint, perfusion cell culture processes in which O.sub.2 /CO.sub.2 containing gases are provided to the cultured cells by a direct means are the methods of choice. Various costly, cumbersome, and complex instrument systems have been developed to operate perfusion and mix/stirred culture systems. While performance improvements can be achieved with such systems, they are invariably dedicated and rather inflexible instruments. Also, the failure rate of these stand alone instruments tend to be relatively high. The primary cause of failure is a malfunction of the hot plate which is typically employed for heating the media reservoir. Reports from users of the heater over shooting the set point and an inability to accurately control the temperature in long-term experiments are not uncommon. Most important of all, the instruments are extremely user unfriendly; often requiring years of experience in order to competently conduct a series of complete procedures without the intervention of a technical expert.
The creation of in vivo-like conditions in cell culture systems is a long-standing challenge. Perfusion and mixed/stirred systems are particularly problematic because cells are exposed to shared forces and other effects related to motion which are not normally experienced in vivo. While attachment factors and extracellular matrix components have become increasing employed in the last 20 years, they remain a research curiosity primarily due to economic reasons. An inexpensive cell culture media additive is required which has general applicability. Such a molecule should fulfill the following three requirements:
(i) enhance cell adhesion in a non-selective way, such that mixing/stirring can proceed efficiently in large scale culture systems;
(ii) manipulations of cells in culture (e.g., genetic transformations) must proceed unimpeded; and,
(iii) culture conditions approaching the cellular environment found in tissues must be advanced.